Fiber materials with improved properties for use in wound treatment

ABSTRACT

Described is a fiber material having a substrate of non-ionic, non-woven fibers, and at least one additional component, which is an agent that comprises at least one group capable of forming a hydrogen bond, wherein the non-ionic, non-woven fibers are crosslinked by the agent. The fiber material can be of use in various fields, in particular household products, hygiene products and the like, these fiber materials are of particular use in wound treatment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is continuation of U.S. application Ser. No.16/480,049, filed on Jul. 23, 2019, which is a U.S. National PhaseApplication of International Application No. PCT/EP2018/051064, filedJan. 17, 2018, which claims priority to European Application No.17153138.7, filed Jan. 25, 2017, each of which are hereby incorporatedby reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to fiber materials with improvedproperties, in particular improved mechanical properties. Theseimprovements, among others, are achieved by providing a substrate ofnon-woven fibers, preferably a web of non-woven fibers, together with anagent having at least one, preferably at least two groups capable offorming a hydrogen bond. The resulting fiber materials have, amongothers, improved tensile strength, in particular wet tensile strength,vis-à-vis fiber materials not treated with such an agent.

While the fiber materials according to the present invention may be ofuse in various fields, in particular as carrier materials, householdproducts, hygiene products and the like, these fiber materials are ofparticular use in wound treatment.

The present invention also relates to a method for producing thesematerials.

BACKGROUND OF THE INVENTION

Fiber materials, in particular fiber materials that are capable toabsorb and retain a liquid (fluid), are useful in a variety ofapplications, including as carrier substrates, household products,hygiene products and in wound treatment. The area of wound treatmentposes particular challenges to fiber materials, since not only isadequate fluid management required, but also integrity of the overallproduct containing the fiber, in particular during application, use andremoval. The fiber material, just as the overall wound care product,must also be sterile, safe to use in contact with bodily fluids and,ideally, comfortable to wear for the patient.

US 2013/0323195 discloses high performance fiber materials, as well asan associated method of production. The document further discloses theuse of such fibers or fibrous structures as carrier materials, hygieneproducts, cosmetic products and bandages or wound dressings, containingsuch fibers or fibrous structures.

An alternative approach to obtain a wound care product, which is notbased on modifying the properties of a fiber material, is realized inGeliperm (Geistlich Pharma AG), which is a hydrogel sheet that consistsof two different interlaced polymers, i.e. an agar gel and apolyacrylamide. The hydrated sheet form contains about 96% water, 1%agar, and 3% polyacrylamide, whereas the dry sheet form differs from thehydrated form that 35% glycerol are added so that the sheet can rapidlyabsorb water (see: “Surgical Dressings and Wound Management”, by StephanThomas, Medetec, 2010).

In order to improve or modify properties of fiber materials used inthese applications, various approaches have been pursued in the art tophysically and/or chemically treat/modify a given fiber material.According to the art, these modifications primarily focus on improvingthe handling properties of the fiber material.

For example, U.S. Pat. No. 2,273,636 discloses regenerated celluloseproducts, obtained from aqueous cellulose solutions, which are treatedwith glycerol derivatives for the purpose of impregnating or softening.In particular, solutions containing 1.5% glycerol-monomethylerther and1.5% triacetine are described for the purpose of softening ofregenerated cellulose products, resulting in soft and elasticcellulose-foils having reduced hygroscopic behavior.

In wound care, fiber materials that are capable of absorbing andretaining fluids are generally preferred over other conceivablesubstrate materials, already for reasons of improved wound exudatemanagement. Fiber materials that are capable to form gels when coming incontact with a fluid, i.e. can take up fluid, are particularlypreferred.

However, wetness and/or swelling (gelling) of the fiber material, andhence the wound care product associated therewith, may lead to problemsregarding the stability/integrity of the wound care product, inparticular the fiber material component thereof. For example, theoverall wound care product may disassociate, either between layers/filmsand/or within a layer/film. Therefore, fiber materials, in particulargel forming fiber materials should ideally maintain their integrityduring use, including during dressing changes, in order to avoiddisintegration, decrease in performance and/or the potential thatresiduals of the dressing remain in the wound.

SUMMARY OF THE INVENTION

In view of the above-mentioned and other drawbacks or unfulfilled needsof the prior art, one object of the present invention is to provide afiber material having improved stability/integrity, in particular inmoist or under wet conditions.

The general concept underlying the present invention is based on therealization that the integrity/stability of a fiber material, inparticular the wet tensile strength of a fiber material as described inmore detail below, can be improved when said fiber material is broughtinto contact with an agent that comprises at least one group capable offorming a hydrogen bond, preferably at least two groups capable offorming a hydrogen bond, resulting in a fiber material that isadvantageously modified.

According to a first aspect of the invention, these and other objectsare achieved by a fiber material comprising:

-   -   a substrate of non-ionic, non-woven fibers, preferably a web of        non-ionic, non-woven fibers,    -   at least one additional component, which is an agent that        comprises at least one group capable of forming a hydrogen bond,        preferably at least two groups capable of forming a hydrogen        bond.

Preferably, the fiber material is capable of absorbing and retaining afluid.

In accordance with the present invention, and in particular in theclaims, the terms “comprising” and “comprise(s)” do not exclude otherelements or steps. Use of the indefinite article “a” or “an” does notexclude a plurality of elements or steps. In particular, more than one(non-ionic or otherwise) type of fiber may be present in the fibermaterial, as well as more than one agent capable of forming a hydrogenbond may be present in the materials of the present invention. Othersuitable materials that are neither fiber materials nor agents capableof forming a hydrogen bond may be present in the fiber materialsaccording to the present invention.

The mere fact that certain measures are recited in mutually differentdependent embodiment or claims does not indicate that a combination ofthese measures cannot be used to advantage.

In accordance with the present invention, a substrate of fibers is anyarrangement of fibers that has a larger extension in a (x-y) plane thanin the direction perpendicular thereto (z-direction). The substrate iscapable to be brought into contact with the at least one agent thatcomprises at least one group capable of forming a hydrogen bond,preferably at least two groups capable of forming a hydrogen bond.Preferably the fiber substrate has an area weight (“grammage”) of 20-500g/m², preferably 50-350 g/m².

In accordance with the present invention, and also in accordance withthe universally accepted understanding of the skilled person, a“non-woven” is defined as sheet or web structures bonded together byentangling fiber or filaments mechanically, thermally, or chemically,but not (as is conventionally done for fabrics) by weaving or knitting.Nonwovens are defined by ISO standard 9092 and CEN EN 29092. Non-wovensubstrates or webs are typically flat, porous sheets that are madedirectly from separate fibers or from molten plastic or plastic films.

In accordance with the present invention, and also in accordance withthe universally accepted definition of the term, a “hydrogen bond” inthe feature “at least one group capable of forming a hydrogen bond” isto be understood as relating to an attractive interaction between ahydrogen atom from a molecule or a molecular fragment X—H in which X ismore electronegative than H, and an atom or a group of atoms in the sameor a different molecule, in which there is evidence of bond formation(see IUPAC Definition for “hydrogen bond” in Pure Appl. Chem., Vol. 83,No. 8, pages 1637-1641, 2011).

As known to the skilled person, and as summarized in the above-mentionedIUPAC reference, a group capable of forming a hydrogen bond can bereadily identified using one or any set of the following officiallyrecognized experimental criteria (E1)-(E6):

-   -   (E1) The forces involved in the formation of a hydrogen bond X—H        ⊇ ⋅ ⋅ Y—Z include those of an electrostatic origin, those        arising from charge transfer between the donor and acceptor        leading to partial covalent bond formation between H and Y, and        those originating from dispersion.    -   (E2) The atoms X and H are covalently bonded to one another and        the X—H bond is polarized, the H ⊇ ⋅ ⋅ Y bond strength        increasing with the increase in electronegativity of X.    -   (E3) The X—H ⊇ ⋅ ⋅ Y angle is usually linear (180°) and the        closer the angle is to 180°, the stronger is the hydrogen bond        and the shorter is the H ⊇ ⋅ ⋅ Y distance.    -   (E4) The length of the X—H bond usually increases on hydrogen        bond formation leading to a red shift in the infrared X—H        stretching frequency and an increase in the infrared absorption        cross-section for the X—H stretching vibration. The greater the        lengthening of the X—H bond in X—H ⊇ ⋅ ⋅ Y, the stronger is the        H ⊇ ⋅ ⋅ Y bond. Simultaneously, new vibrational modes associated        with the formation of the H ⊇ ⋅ ⋅ Y bond are generated.    -   (E5) The X—H ⊇ ⋅ ⋅ Y—Z hydrogen bond leads to characteristic NMR        signatures that typically include pronounced proton deshielding        for H in X—H, through hydrogen bond spin-spin couplings between        X and Y, and nuclear Overhauser enhancements.    -   (E6) The Gibbs energy of formation for the hydrogen bond should        be greater than the thermal energy of the system for the        hydrogen bond to be detected experimentally.

In an embodiment of the present invention, the agent that comprises atleast one group capable of forming a hydrogen bond, preferably at leasttwo groups capable of forming a hydrogen bond, comprises at least one ofthe following groups: hydroxyl groups (OH), carboxyl groups (COOH),amino groups (NH), sulfhydryl groups (SH) and/or hydrogen donor linkagesthat include, but are not limited to, glycolytic linkages, peptidebonds.

Preferably, these groups are hydroxyl groups, amino groups or sulfhydrylgroups.

In accordance with the present invention, the term “fiber” is to beunderstood as generally referring to threads or threadlike structuresand is generally understood to relate to a flexible structure, which isthin in relation to its length. Fibers have a small diameter and can bebuilt up with one another by corresponding bonding processes to producefibrous structures or fiber materials. In accordance with the presentinvention, the average diameter of the fibers making up the fibermaterial is preferably in the range of 50 nm to 1000 μm, preferably 1 μmto 100 μm, further preferably from 5-25 μm.

In accordance with the present invention, the fiber material comprisesat least one non-ionic fiber material. A “non-ionic” fiber, inaccordance with the present invention, describes a fiber that issubstantially not ionizing in aqueous solution at a pH value of 7.

In embodiments of the invention, the amount of agent in the fibermaterial, relative to the overall weight of the composite material, isfrom 1% w/w to 40% w/w, preferably from 5% w/w to 35% w/w, furtherpreferably from 15% w/w to 25% w/w.

In embodiments of the invention, the wet tensile strength (as definedbelow) of the fiber material is increased by at least 5%, preferably atleast 10% and further preferably by at least 15%, for a fiber materialaccording to the present invention, compared to an otherwise identicalfiber material, which, however, has not been treated with the at leastone agent.

In embodiments of the invention, the fiber material comprises anantimicrobial agent, in particular the fiber material comprises:

-   -   a substrate of non-ionic, non-woven fibers, preferably a web of        non-ionic, non-woven fibers,    -   at least one additional component, which is an agent that        comprises at least one group capable of forming a hydrogen bond,        preferably at least two groups capable of forming a hydrogen        bond,    -   at least one antimicrobial agent.

In accordance with the present invention, the antimicrobial agent may beapplied, or may be present in the final product, together with the agenthaving at least one, preferably two groups capable of forming a hydrogenbond. Therefore, the overall fiber material is homogenously improved notonly in regard to integrity in the wet state, but also particularlysuited for wound treatment.

In embodiments of the invention, the antimicrobial agent comprisessilver. In embodiments of the invention, the silver is metallic silver.In embodiments of the invention, the silver is a silver salt. Inembodiments of the invention, the silver salt is silver sulfate, silverchloride, silver nitrate, silver sulfadiazine, silver carbonate, silverphosphate, silver lactate, silver bromide, silver acetate, silvercitrate, silver CMC, silver oxide. In embodiments of the invention, thesilver salt is silver sulfate. In embodiments of the invention, theantimicrobial agent comprises a monoguanide or biguanide. In embodimentsof the invention, the monoguanide or biguanide is chlorhexidinedigluconate, chlorhexidine diacetate, chlorhexidine dihydrochloride,polyhexamethylene biguanide (PHMB) or a salt thereof, orpolyhexamethylene monoguanide (PHMG) or a salt thereof. In embodimentsof the invention, the biguanide is PHMB or a salt thereof. Inembodiments of the invention, the antimicrobial agent comprises aquaternary ammonium compound. In embodiments of the invention, thequaternary ammonium compound is cetylpyridinium chloride, benzethoniumchloride, or poly-DADMAC. In embodiments of the invention, theantimicrobial agent comprises triclosan, sodium hypochlorite, copper,hydrogen peroxide, xylitol, or honey.

In embodiments of the invention, the fiber material further comprises anantimicrobial coating that comprises an antimicrobial agent and one ormore polymers, wherein the one or more polymers are selected from thegroup consisting of cellulosic polymers, neutral poly(meth)acrylateesters, polyvinylpyrrolidone, polyvinylpolypyrrolidone, and combinationsthereof.

In embodiments of the invention, the fiber material comprises polyvinylalcohol, preferably wherein the polyvinyl alcohol is cross-linked.

In embodiments of the invention, the one or more polymers in theantimicrobial coating are cellulosic polymers, preferably selected fromthe group consisting of hydroxypropylmethylcellulose (HPMC),hydroxypropylcellulose (HPC), methylcellulose (MC), and ethylcellulose(EC), preferably hydroxypropylcellulose (HPC). In embodiments of theinvention, the one or more polymers in the antimicrobial coating ishydroxypropylcellulose (HPC).

In embodiments of the invention, the antimicrobial agent in theantimicrobial coating is or comprises silver, preferably silver oxide ora silver salt.

In embodiments of the invention, the fiber material further comprises atleast one absorbing material, preferably a superabsorbent material,further preferably superabsorbent polymers, further preferably in theform of particles.

The presence of such an (additional) absorbing material allows tofurther control fluid uptake and management capabilities of the fibermaterial, which is particularly advantageous in wound treatment.

According to a second aspect of the invention, the above-discussed andother objects are achieved through a process for making a fibermaterial, comprising the following steps:

-   -   providing at least one non-ionic fiber material, this is present        in a non-woven substrate, preferably in a non-woven web;    -   bringing said at least one non-ionic fiber material into contact        with at least one agent that comprises at least one group        capable of forming a hydrogen bond, preferably at least two        groups capable of forming a hydrogen bond.

In embodiments of the invention, said process also comprises thefollowing step, which is performed after the “bringing intocontact”-step above:

-   -   drying the non-ionic fiber material and the agent as brought        into contact with each other.

Preferably, said agent that is brought into contact with at least onenon-ionic fiber material, is provided as a compound that is dissolved ordistributed in a liquid, in particular in form of a solution, a slurry,an emulsion or the like. In accordance with the present invention, it isparticularly preferred if the agent (compound) is present as a solute ina solvent.

However, the direct application of the agent (compound), without asolvent, including in solid form, is also within the scope of thepresent invention.

In regard to the solvent, no restrictions or limitations exist, exceptthat the solvent must be able to dissolve the agent and the solvent doescause irreversible swelling of the non-ionic fiber material during orafter application. Examples of such solvents are, but are not limitedto, ethanol, isopropanol and methanol. Ethanol is a preferred solvent.

In accordance with the present invention, the term “bringing intocontact” is to be understood to generally relate to methods known to theperson skilled in the art as relating to bringing a solid material intophysical contact with another material, which may be a solid or a fluid.Examples of such ‘bringing into contact’ include, but are not limitedto: applying a solid or viscous substance by (spray) deposition,calendering, coating, dipping etc. or applying and/or spraying a fluidmedium onto a (fiber) material, dipping the (fiber) material into afluid medium, saturating/soaking of the (fiber) material in a fluidmedium, or forming a slurry, suspension or mixture of the (fiber)material with a fluid medium. The fluid medium may for example be amixture (e.g. suspension or solution) of the agent and at least one ofthe above discussed solvents.

In accordance with the present invention, it is particularly preferredthat the fiber material is impregnated with the at least one agentand/or that the at least one agent is applied onto the fiber material.

In one embodiment of the invention, the fiber material as brought intocontact with the at least one agent is exposed to an atmosphere with apartial pressure of the fluid medium lower than the pressure of the pureliquid (i.e. the fluid medium), so that the fluid medium, at leastpartly, evaporates. Such a lowered pressure can be achieved by means ofapplying a lowered pressure, including vacuum, for example.

In accordance with the present invention, the ‘drying’-step may occurunder ambient conditions (i.e. at atmospheric pressure and roomtemperature), preferably for 6 to 12 hours, or may occur at elevatedtemperature and/or under reduced pressure.

The fiber materials according to the invention exhibit improvedproperties vis-à-vis known fiber materials. While the fiber materials inaccordance with the present invention may not show all of the potentialimprovements discussed in the following, or not all to the same extentor to the fullest extent, the following improvements are generally foundin materials in accordance with the present invention.

As already alluded to above, the integrity of fiber materials in the wetstate is of particular importance. One way to measure this ‘integrity’or ‘stability’ is to measure the wet tensile strength (as defined inmore detail below) of such a fiber material.

The inventors have found that the fiber materials according to thepresent invention, comprising at least one additional component(additional to the non-ionic fiber material), which is an agent thatcomprises at least one group capable of forming a hydrogen bond,preferably at least two groups capable of forming a hydrogen bond,wherein the non-ionic fiber material and the agent are linked by meansof hydrogen bonds, have increased wet tensile strength vis-à-vis anotherwise identical fiber material, which, however, does not comprisesaid agent, and/or has not been brought into contact with said agent.

Without wishing to be bound by theory, the inventors believe that theimproved (mechanical) properties of a non-ionic fiber material, in whichthe non-ionic fiber material has been brought into contact with (treatedwith) the at least one agent comprising at least one, preferably two,group(s) capable of forming a hydrogen bond is due to the formation ofhydrogen bonds between the backbone of the polymer making up the fibermaterial and the hydrophilic groups of the agent. This mechanism isbelieved to contribute to improved properties, such as improved wetstrength, gelling speed and keeping the product from drying out tooquickly. This effect is schematically illustrated for stabilizing a PVAbackbone by way of forming hydrogen bonds with glycerol (see FIG. 1 ).

The term “wet tensile strength” is to be understood as the maximumtensile force per unit width, as measured in accordance with EN29073-3:1992 (with amendments as specified below), that a test piecewill stand, in a wet state having absorbed a maximum amount of SolutionA according to the “Free swell absorptive capacity method” EN 13726-1(with an absorption time of 10±1 minutes at 23±2° C.), before it breaksapart in said tensile strength test.

The method of measuring the “wet tensile strength”, according to theinvention, is modified vis-à-vis EN 29073-3:1992 in the followingmanner: i) the material is soaked according to EN 13726-1 (with anabsorption time of 10±1 minutes at 23±2° C. and before cutting the testpiece); ii) the test piece is cut according to FIG. 2 giving a width of20 mm; iii) a gauge length of 50 mm (i.e. distance between jawsaccording to section 7.2 of EN 29073-3:1992) is used; and iv) method isperformed at a temperature of 23±2° C. and 50±5% rh. These deviationsare all allowable alterations of EN 29073-3:1992 (see, e.g., notes insections 6 and 7 of EN 29073-3:1992).

Solution A, as defined in EN 13726-1, consists of a sodium chloride andcalcium chloride solution containing 142 mmol of sodium ions and 2.5mmol of calcium ions as the chloride salts. This solution has an ioniccomposition comparable to human serum or wound exudate. Said solution isprepared by dissolving 8,298 g of sodium chloride and 0,368 g of calciumchloride dihydrate in deionized water up to the “1 L” marking in avolumetric flask.

According to another aspect, products comprising gel-forming fibermaterials, i.e. fiber materials that expand when exposed to fluids, mayget stiff(er) when they dry out, for example due to a decreased flow ofwound exudate. This may cause discomfort and/or pain to the patient,especially during dressing changes. The inventors have found that thefiber materials according to the present invention, comprising at leastone additional component (additional to the non-ionic fiber material),which is an agent that comprises at least one group capable of forming ahydrogen bond, preferably at least two groups capable of forming ahydrogen bond, wherein the non-ionic fiber material and the agent arelinked by means of hydrogen bonds, are less likely to get stiff and aretherefore perceived to be “softer” and more comfortable for the patientcompared to the otherwise identical fiber material that does notcomprise said agent and/or has not been brought into contact with saidagent.

In embodiments of the invention and in order to efficiently absorbexudate, the non-ionic fiber material should be at least partlyhydrophilic. In case the starting materials are not (sufficiently)hydrophilic, in particular if the fiber material appears to not absorbwater rapidly enough, also in regard to its macroscopic behavior, insome embodiments the fiber material is treated to be (more) hydrophilic,for example by means of plasma treatment. Under certain circumstances,this treatment may lose its effectiveness over time. The inventors havefound that the fiber materials according to the present invention,comprising at least one additional component (additional to thenon-ionic fiber material), which is an agent that comprises at least onegroup capable of forming a hydrogen bond, preferably at least two groupscapable of forming a hydrogen bond, are less likely to lose hydrophilicproperties over time-of-use, compared to the otherwise identical fibermaterial that does not comprise said agent, and/or has not been broughtinto contact with said agent.

In accordance with the present invention, the term “hydrophilic” is tobe understood as defined in IUPAC: Compendium of Chemical Terminology,2nd ed. (the “Gold Book”), compiled by A. D. McNaught and A. Wilkinson.Blackwell Scientific Publications, Oxford (1997), ISBN 0-9678550-9-8, asgenerally referring to the capacity of a molecular entity or of asubstituent to interact with polar solvents, in particular with water,or with other polar groups.

Wound dressings comprising hydrophilic fiber materials known from theart may not form a gel instantly, or not as fast as desired. This isgenerally perceived as a disadvantage. The inventors have found that thefiber materials according to the present invention have improvedgel-forming properties compared to an otherwise identical fiber materialthat does not comprise an agent that comprises at least one, preferablytwo groups capable of forming a hydrogen bond, and/or has not beenbrought into contact with said agent.

While the present invention is primarily exemplified and illustrated inthe context of wound treatment/wound care, the fiber materials of thepresent invention are generally suitable for all uses, in which fibermaterials of increased strength and integrity are advantageous, includedbut not limited to use as substrate/carrier materials, use in householdproducts and use in cosmetics or hygiene articles, for examples femalehygiene articles, diapers, absorbent pads etc.

Therefore, in a third aspect, the present invention relates to a fibermaterial in accordance with the present invention, or produced inaccordance with the present invention, as or in substrate/carriermaterials, for use in household products, for use in cosmetics orhygiene articles, in particular female hygiene articles, diapers,absorbent pads, or for use in wound treatment.

The use in wound care/wound treatment, includes the care/treatment ofopen or closed wounds, for example, including, inter alia (but notlimited to), chronic wounds, acute wounds, and post-operative woundssuch as e.g. closed incisions or scar treatment.

The fiber materials of the present invention are capable to absorb andretain a liquid and may be used ‘stand-alone’ [i.e. without the presenceof another (super)absorbent] material, in any uses requiring absorptioncapabilities. However, in embodiments of the present invention, thefiber materials are used together with an additional absorbing material,in particular superabsorbent materials, in particular superabsorbentpolymers, preferably in the form of particles.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Without limitation, suitable non-ionic fiber materials include or arepolyvinyl alcohol, polysaccharides, and polymers comprising polyethyleneglycol (PEG) and/or polypropylene glycol, for example polyurethane withPEG functionalities, such as the polymer fibers disclosed in WO2013/041620.

In some embodiments, the non-ionic fiber material is or comprises apolyvinyl alcohol. In some embodiments the non-ionic fiber materialscomprises a plurality of fibers comprising polyvinyl alcohol, such asthe plurality of fibers disclosed in US 2013/0323195 and/or US2013/0274415, the content of which relating to fiber materials is herebyincorporated by reference.

In some embodiments, the non-ionic fiber material comprises apolyurethane polymer with polyethylene glycol (PEG) and/or polypropyleneglycol functionalities, such as the polymer fibers disclosed in WO2013/041620.

In preferred embodiments of the present invention, said non-ionic fibermaterial is or comprises polyvinyl alcohol. At least one polyvinylalcohol copolymer may also be used. In the case of a polyvinyl alcoholcopolymer, polyethylene vinyl alcohol may be used, for example.

If polyvinyl alcohol copolymers are used as non-ionic fiber materials,the properties of the fibers may be adjusted in a targeted manner asappropriate. Thus in the event of use of, for example polyethylene vinylalcohol, the number of OH groups may be reduced. However, otherfunctional groups may also be introduced into the fibers by means ofcopolymerisation. Thus, polyvinyl alcohol copolymers make furthernon-ionic fiber materials available.

Polyethylene vinyl alcohol, polyvinyl alcohol styrene, polyvinyl alcoholvinyl acetate, polyvinyl alcohol vinyl pyrrolidone, polyvinyl alcoholethylene glycol and/or polyvinyl alcohol, particularly preferablypolyethylene vinyl alcohol, polyvinyl alcohol vinyl acetate, polyvinylalcohol vinyl pyrrolidone, polyvinyl alcohol vinylamine, polyvinylalcohol acrylate, polyvinyl alcohol acrylamide, polyvinyl alcoholethylene glycol and/or polyvinyl alcohol and particularly preferablypolyvinyl alcohol may all be used as a non-ionic fiber material, inaccordance with the present invention. Block copolymers and/or graftcopolymers and/or block and graft copolymers, statistical or alternatingsystems and any mixtures of these are used as non-ionic fiber material.

A polyvinyl alcohol copolymer may be used in unsubstituted or inpartially substituted form. In the event of partial substitution,partial substitution of the OH groups by —O(C═O)—R or —OR is included,wherein R, in each case independently of one another, stands for a C1-C4alkyl group. In this case a C1-C4 alkyl group is understood to bemethyl, ethyl, propyl, iso-propyl, 1-butyl, 2-butyl, or tert-butyl.

Furthermore the non-ionic fiber material may be formed as a polymerblend. In this case a polymer blend is understood to be a physicalmixture of at least two polymers from the melt or from the solution.

In order to form such a polymer blend, further polymers may be used,such as for example alginates, cellulose ethers, such as carboxymethylcelluloses, methyl celluloses, ethyl celluloses, hydroxymethylcelluloses, hydroxyethyl celluloses, hydroxyalkyl methylcelluloses,hydroxypropyl celluloses, cellulose esters, such as cellulose acetate,oxidised celluloses, bacterial celluloses, cellulose carbonates,gelatines, collagens, starches, hyaluronic acids, pectins, agar,polyacrylates, polyvinyl amines, polyvinyl acetates, polyethyleneglycols, polyethylene oxides, polyvinyl pyrrolidones, polyurethanes ornongelling further polymers, such as for example polyolefins,celluloses, cellulose derivatives, regenerated celluloses such viscoses,polyamides, polyacrylonitriles, polyvinyl chlorides, chitosans,polylactides, polyglycolides, polyester amides, polycaprolactones,polyhexamethylene terephthalates, polyhydroxybutyrates,polyhydroxyvalerates or polyesters.

In some embodiments, the non-ionic fiber material comprises a polymerthat is cross-linked, in particular cross-linked polyvinyl alcohol. Theterm “cross-linked” is used herein to describe a material comprising aplurality polymer molecules which are interlinked by a chemical bond, inparticular a covalent bond or an ionic bond, or by a physicalcross-link, such as in thermoplastic elastomers.

In some embodiments, the non-ionic fiber material is cross-linked byheat or chemical treatment, in particular by heat. Cross-linkednon-ionic fiber materials are capable of forming a swollen coherent gelupon absorbing a liquid. Thereby, a wound dressing substrate comprisingsuch a fiber material can be removed coherently from a wound. Usingnon-ionic fiber material that is (already) crosslinked is in accordancewith the present invention, in regard to which it is believed (seediscussion below) that the bringing into contact of the non-ionic fibermaterial with the at least one agent comprising one, preferably two,group(s) capable of forming a hydrogen bond, results in (further)crosslinking of the non-ionic fiber material.

Overall, in embodiments of the present invention, the non-ionic fibermaterial comprises or consists of polyvinyl alcohol (PVA), preferablycross-linked PVA, polysaccharides, and/or polyurethane polymer withpolyethylene glycol (PEG) and/or polypropylene glycol functionalities,and/or copolymers thereof.

In some embodiments, a fiber material according to the presentinvention, in particular a wound dressing substrate comprising the fibermaterial according to the present invention, in a wet state havingabsorbed a maximum amount of Solution A according to EN 13726-1 (with anabsorption time of 10±1 minutes and at a temperature of 23±2° C.), has awet tensile strength of at least 0.2 N/2 cm as measured by EN29073-3:1992 (with the modifications as specified above).

In some embodiments, the fiber material according to the presentinvention, in particular a wound dressing substrate in a wet state asdefined above, has a wet tensile strength (as defined above) of at least0.2 N/2 cm preferably at least 0.6 N/2 cm or at least 0.8 N/2 cm or atleast 1.0 N/2 cm, or at least 1.5 N/2 cm, or at least 2 N/2 cm, furtherpreferably at least 2.5 N/2 cm, or at least 3 N/2 cm, for example atleast 4 N/2 cm such as at least 5 N/2 cm or at least 6 N/2 cm or atleast 7 N/2 cm or at least 8 N/2 cm or at least 9 N/2 cm, or at least 10N/2 cm, further preferably at least 15 N/2 cm such as at least 20 N/2 cmor at least 25 N/2 cm. Fulfilling such “minimal” requirements for thewet tensile strength is of particular importance in wound treatment,where disintegration of a wound dressing when wet is a situation thatshould be avoided.

In some embodiments, the fiber material according to the presentinvention, in particular a wound dressing substrate in a wet state asdefined above, has a wet tensile strength (as defined above) of from 0.2to 15 N/2 cm. In some embodiments, the fiber material according to thepresent invention, in particular the wound dressing substrate in a wetstate, has a wet tensile strength (as defined above) of from 1 to 10 N/2cm. In some embodiments, the fiber material according to the presentinvention, in particular the wound dressing substrate in a wet state asdefined above, has a wet tensile strength (as defined above) of from 2to 10 N/2 cm.

As used herein, the term “wound dressing substrate in a wet state”,should be understood as a wound dressing substrate which has been wetted(or soaked) to maximum absorptive capacity according to EN 13726-1:2002(with absorption time of 10±1 minutes and at a temperature of 23±2° C.).Thus, the tensile strength as given herein refers to the tensilestrength as measured on such wet wound dressing substrate and/or on afiber material according to the present invention.

In some embodiments, the wet tensile strength (as defined above) isincreased by at least 5%, preferably at least 10% and further preferablyby at least 15%, for a fiber material according to the presentinvention, compared to an otherwise identical fiber material, which,however, has not been treated with the at least one agent comprising atleast one group capable of forming a hydrogen bond, preferably at leasttwo groups capable of forming a hydrogen bond.

In principle, no limitation exist in regard to the agent that comprisesat least one group capable of forming a hydrogen bond, preferably atleast two groups capable of forming a hydrogen bond. Said agent ispreferably a compound, which compound can either be a monomer/smallmolecule or a polymer.

In some embodiments, the agent that comprises at least one group capableof forming a hydrogen bond, preferably at least two groups capable offorming a hydrogen bond, is selected from the group consisting ofpolyols, in particular sugar alcohols (sugar polyols), polymericpolyols; polysaccharides, alpha-hydroxy acids; cellulose ethers orcellulose esters; di- or polyisocyanates; polyethers or polyesters.

Non-limiting examples of such agents are: glycol, propylene glycol,glycerol, sorbitol, xylitol, maltitol, hexylene glycol, butylene glycol,glyceryl triacetate, polydextrose, lactic acid, panthtothenic acid,hyaluronic acid, sodium-2-pyrrolidone-5-carboxylate (′sodium PCA′),polyethylene glycol (PEG) (also known as polyethylene oxide orpolyoxyethylene), polypropylene glycol (PPG), polyvinylpyrrolidone(PVP), (also known as polyvidone or povidone).

In some embodiments, the agent that comprises at least one group capableof forming a hydrogen bond, preferably at least two groups capable offorming a hydrogen bond, is glycerol or polyethylene glycol.

As already discussed above, the non-ionic fibers in accordance with thepresent invention preferably increase in fiber diameter upon contactwith a fluid/moisture, i.e. gel during use and/or at the point of use. Agel should be understood to be a finely dispersed system consisting ofat least one solid and one liquid phase, wherein the solid phase forms athree-dimensional network the pores of which are filled by the liquidphase. Both phases penetrate one another essentially completely andconsequently may store a liquid phase, for example an exudate, in a morestable manner with respect to, for example, pressure. Fibers or fibrousstructures according to the present invention are preferably chosen tobe gelling, in particular hydrogelling, and consequently have anoutstanding retention capacity for corresponding liquid phases. Fibersor fibrous structures according to the present invention are preferablyapplied in a dry state to the wound and they form stable gels with thewound exudate, thus creating a moist wound climate. Such a moist woundtreatment may assist the healing process.

Likewise, for moist wound treatment fibers or fibrous structuresaccording to the present invention can be used in gel form with a liquidphase. In this case water is preferably used as liquid phase andparticularly preferably a 0.9% aqueous sodium chloride solution, Ringersolution or solutions containing an active substance. Consequentlygelling should be understood as the ability to form a gel by absorbing aliquid phase, and hydrogelling should be understood as the ability toform a hydrogel, which has as liquid phase water or an aqueous solution,particularly preferably a 0.9%, aqueous sodium chloride solution.

In some embodiments of the invention, the fiber material in accordancewith the present invention has a free swell absorptive capacity,corresponding to the maximum absorptive capacity of the fiber materialin accordance with the present invention, of at least 1 times its ownweight as measured by EN 13726-1:2002 (“Free swell absorptivecapacity”). For example, in some embodiments, the fiber material inaccordance with the present invention has a free swell absorptivecapacity, corresponding to the maximum absorptive capacity of the fibermaterial in accordance with the present invention, of at least 3 timesits own weight as measured by EN 13726-1:2002. For example, in someembodiments, the fiber material in accordance with the present inventionhas a free swell absorptive capacity, corresponding to the maximumabsorptive capacity of the fiber material in accordance with the presentinvention, of at least 5 times its own weight as measured by EN13726-1:2002. For example, in some embodiments, the fiber material inaccordance with the present invention has a free swell absorptivecapacity, corresponding to the maximum absorptive capacity of the fibermaterial in accordance with the present invention, of at least 10 timesits own weight as measured by EN 13726-1:2002. For example, in someembodiments, the fiber material in accordance with the present inventionhas a free swell absorptive capacity, corresponding to the maximumabsorptive capacity of the fiber material in accordance with the presentinvention, of at least 15 times its own weight as measured by EN13726-1:2002. For example, in some embodiments, the fiber material inaccordance with the present invention has a free swell absorptivecapacity, corresponding to the maximum absorptive capacity of the fibermaterial in accordance with the present invention, of at least 20 timesits own weight as measured by EN 13726-1:2002. For example, in someembodiments, the fiber material in accordance with the present inventionhas a free swell absorptive capacity, corresponding to the maximumabsorptive capacity of the fiber material in accordance with the presentinvention, of at least 25 times its own weight as measured by EN13726-1:2002.

In some embodiments, the substrate comprises absorbent particles. Insome embodiments, the absorbent particles are dispersed within the fibermaterial. In some embodiments, the substrate also includes non-absorbentfibers. In some embodiments, the absorbent fibers and/or absorbentparticles are airlaid by spraying, needling, or carding together withnon-absorbent fibers.

The advantages of the invention have been demonstrated in the followingExamples.

EXAMPLES Example 1— Preparation of Samples

Formulations, as outlined in Table 1, were prepared by adding arespective amount of each agent, including glycerol (commerciallyavailable from Sigma-Aldrich), PEG 200 (commercially available from AlfaAesar), and PEG 400 (commercially available from Alfa Aesar), to ethanol(200 proof, commercially available from Merck). The formulations werestirred for 15 minutes at room temperature.

Exufiber® (commercially available from Mölnlycke Health Care; size:20×30 cm, 250 gsm), which is a non-ionic and nonwoven fiber dressingcomprising (non-ionic) crosslinked polyvinyl alcohol fibers, was treatedwith the different formulations by adding the formulation (0.15 g/cm²)using a pipette to thereby produce samples with the different agents atincreasing concentrations of agents as disclosed in Table 1.Subsequently, the samples were dried at room temperature for 3 days(before further testing according to Example 2, see below).

In addition, Aquacel® (commercially available from ConvaTec, size: 15×15cm, 100 gsm), which a nonwoven but ionic (charged) fiber dressingcomprising carboxymethyl cellulose (CMC) fibers in ionic form (e.g. asthe sodium salt), was treated (0.15 g/cm²) using a pipette with theglycerol formulations, and subsequently dried at room temperature for 3days, to produce Aquacel® test samples comprising glycerol at differentconcentrations, as disclosed in Table 1. References samples with bothExufiber® and Aquacel® was also prepared, without adding the agentaccording to the present invention but instead treated accordingly with100% ethanol and subsequently dried.

Example 2

The wet tensile strength was tested according to the following method:samples (size should be large enough to fit the punching tool afterpossible shrinkage on absorption) were prepared as described above (seeexample 1) and were first allowed to absorb (for 10±1 min) a maximumamount of Solution A according to EN 13726-1:2002. The samples wereplaced on a cutting board and punched out, in nonwoven machinedirection, with a necking punch according to FIG. 2 . The wet tensilestrength of the samples was measured using a tensile testing instrument(Zwick Z005 TE) with a cross head speed of 100 mm/min and a gauge lengthof 50 mm.

The result of the wet tensile strength testing according to Example 2 isshown in Table 1 below. Each testing was performed in triplicate,respectively, and the value presented in Table 1 is thus the calculatedaverage value.

TABLE 1 Formulations Agent conc. in Wet tensile Test (% w/w agent driedtest sample strength Sample in EtOH) (% w/w) (N/20 mm) 1 0% agentExufiber ® 2.27N/20 mm (100% EtOH) (no agent added) 2 Glycerol; 1.45%Exufiber ® 8% glycerol 2.37N/20 mm 3 Glycerol; 4.16% Exufiber ® 20%glycerol 2.94N/20 mm 4 Glycerol; 8.97% Exufiber ® 35% glycerol 3.71N/20mm 5 PEG200; 8.97% Exufiber ® 35% PEG200 3.10N/20 mm 6 PEG400; 8.97%Exufiber ® 35% PEG400 3.29N/20 mm 7 0% agent Aquacel ® 0.38N/20 mm (100%EtOH) (no agent added) 8 Glycerol; 1.67% Aquacel ® 20% glycerol 0.32N/20mm 9 Glycerol; 3.59% Aquacel ® 35% glycerol 0.38N/20 mm

As can be seen, for the Exufiber® nonwoven fiber dressing, addingglycerol surprisingly improved the wet tensile strength of the fiberssignificantly with an increase of 4.4% for 8% w/w glycerol, 29.5% for20% w/w glycerol, and 63.4% for 35% w/w glycerol, as compared with thetensile strength of the reference Exufiber® sample (no agent). Also, thetest samples with 35% w/w PEG200 and 35% w/w PEG400 showed a significantand equally surprisingly improved wet tensile strength with an increaseof 36.5% and 44.9%, respectively. In contrast, the Aquacel® samplestreated with glycerol (20% w/w and 35% w/w, respectively) did not resultin an increased wet tensile strength.

Without wishing to be bound by theory, it is believed that the non-ionicnature of the crosslinked polyvinyl alcohol fibers facilitates chemicalinteraction with the agent, for example, by hydrogen bonding interactionbetween the hydroxyl groups on the polyvinyl alcohol fiber and thehydroxyl groups of the agents, thus creating hydrogen bonding bridges(e.g. cross-linkages) between polyvinyl alcohol polymer chains in thefibers.

Example 3

Gelling time was measured using a stop watch by visual inspection of thesamples 1 to 4 (prepared as described above) after soaking in Solution Aaccording to EN 13726-1:2002. The stop watch was started at the sametime as the sample was soaked. When the samples turned into atransparent gel from their original fibrous state the time was recorded.

As can be seen in Table 2, impregnation of Exufiber® with the agent inaccordance with the present invention significantly reduces the gel timein contact with aqueous solution. Thereby, faster absorption isachieved.

TABLE 2 Sample Gelling time 1: Exufiber ® (no agent added) 27 sec 2:Exufiber ® 8% glycerol 15 sec 3: Exufiber ® 20% glycerol 12 sec 4:Exufiber ® 35% glycerol 11 sec

All Examples 1 to 3 were performed at a temperature of 23±2° C. and50±5% relative humidity.

1. A fiber material comprising: a substrate of non-ionic, non-wovenfibers, and at least one additional component, which is an agent thatcomprises at least one group capable of forming a hydrogen bond, whereinthe non-ionic, non-woven fibers are crosslinked by the agent.
 2. Thefiber material according to claim 1, wherein the non-ionic, non-wovenfibers comprises polyvinyl alcohol (PVA), a polysaccharide, and/or apolyurethane polymer with polyethylene glycol (PEG) and/or polypropyleneglycol functionalities, and/or copolymers thereof.
 3. The fiber materialaccording to claim 1, wherein the agent that comprises the at least onegroup capable of forming a hydrogen bond comprises at least one of thefollowing groups: a hydroxyl group, a carboxyl group, an amino group, asulfhydryl group, and/or hydrogen donor linkages comprising a glycolyticlinkage, or a peptide bond.
 4. The fiber material according to claim 1,wherein the amount of agent in the fiber material, relative to theoverall weight of the fiber material, is from 1% w/w to 40% w/w.
 5. Thefiber material according to claim 1, further comprising at least oneantimicrobial agent.
 6. The fiber material according to claim 1, furthercomprising at least one absorbing material.
 7. The fiber materialaccording to claim 1, wherein the wet tensile strength of the fibermaterial is increased by at least 5%, as compared to an otherwiseidentical fiber material without the at least one agent comprising theat least one group capable of forming a hydrogen bond.
 8. The fibermaterial according to claim 1, wherein the substrate of non-ionic,non-woven fibers is a web of non-ionic, non-woven fibers.
 9. The fibermaterial according to claim 1, wherein the substrate of non-ionic,non-woven fibers comprises cross-linked PVA.
 10. The fiber materialaccording to claim 1, further comprising at least one superabsorbentmaterial in the form of particles.
 11. The fiber material according toclaim 1, wherein the amount of agent in the fiber material, relative tothe overall weight of the fiber material, is from 15% w/w to 25% w/w.12. The fiber material according to claim 1, wherein the agent comprisesat least two groups capable of forming a hydrogen bond.
 13. A processfor making a fiber material comprising the following steps: providing atleast one non-ionic fiber material, which is present as a non-wovensubstrate; bringing said at least one non-ionic fiber material intocontact with at least one agent that comprises at least one groupcapable of forming a hydrogen bond, thereby crosslinking the non-ionicfiber material by the agent.
 14. The process according to claim 13,further comprising the following step: drying the non-ionic fibermaterial and the agent as brought into contact with each other.
 15. Theprocess according to claim 13, wherein the at least one agent thatcomprises the at least one group capable of forming a hydrogen bond andthat is brought into contact with at least one non-ionic fiber materialis provided as a compound that is dissolved or is distributed in aliquid.